1. Field of the Invention
The invention relates to an anchoring shaft for a joint endoprosthesis. More specifically, the anchoring shaft is used in a hip joint prosthesis.
2. Description of Related Art
An anchoring shaft is disclosed in EP-A-0 427 902. The shaft disclosed in the European application includes a femoral head prosthesis. The cross-section of the shaft is square in the distal or lower half. The proximal or upper half of the shaft has a rounded rectangular or oval shape. The shaft widens conically on all sides of the shaft starting from the distal end.
The European application prefers a square shaped shaft at the distal end, since semicircular interstices establish areas where cancellous bone tissue can form and revascularization of the bone takes place. The edges of the lower half of the shaft are provided with sawtooth-shaped teeth. The points of the teeth lie on an edge and are slightly set back. The teeth are short with a very small tooth depth, so an approximate square cross-section of the shaft is retained. The teeth are provided in rows and point in a medial direction. The teeth of some rows can be designed so they perform a cutting action. The teeth in other tooth rows are designed so they do not cut, but merely displace bone tissue. Accordingly, the supporting action of the square shaft along the edges is maintained.